The present invention relates to a tooth replacement, which has an implant member, and to the forming thereof.
Dental implants are known. Generally, the process of installing an implant is performed in two steps. During the first step, a bore is drilled vertically through the jawbone. The jawbone is formed of a hard, cortical exterior and a cancellous, sponge-like interior. In a sense, the jawbone can be envisioned as hard crest and side plates that encase the cancellous interior. The bore is drilled through the cortical crest and into the cancellous interior. A generally cylindrical implant member is fitted into the bore, so that its top portion reaches the bone crest. The cylindrical implant member may be a bullet-like cylinder, which has a smooth surface, and which is press-fitted into the bore. Alternatively, the cylindrical implant member may have screw threads around its external surface so as to self-tap its way into the bore. The implant member includes a support structure, for example, a threaded cervix, for supporting a dental prosthesis. During the first step, the cervix is sealed. The bone is then allowed to heal, as the cancellous interior grows around the implant. Often, the implant member is coated with a bone-growth enhancing material, to induce the healing process, which may take several months. During the second step, after healing, the sealant is removed from the support structure of the implant member, and a second member, a dental prosthesis having a crown, which serves as an artificial tooth, and a post, is secured onto the implant member. The post is preformed or cast individually, for example, as a threaded stud that substantially matches the threaded cervix of the implant member. The crown is then cemented onto the post.
A few of the factors, which determine the success of the implant, are as follows:
1. Depth of the bore: For good anchoring, a relatively deep bore of 10-16 mm is generally required. However, for some people, especially older people, a bore deeper than 5 or 6 mm on the lower jaw may make contact with the mandibular canal. For these people, good anchoring with respect to the cancellous bone tissue cannot be achieved.
2. Bacterial penetration: The penetration of bacteria poses additional risk to the bone tissue, and can also lead to local mortality and implant failure. Generally, when the bone heals around the implant member, and the gingival tissue closes on it, there is no bacterial penetration along the interface between the implant member and the bone. However, when the dental prosthesis is installed, the interface surface between the crown and the post, on the one hand, and the implant member support structure, such as the threaded cervix, on the other hand, is susceptible to bacterial penetration.
3. Trauma to the cancellous bone tissue: Excessive vertical or lateral forces by the implants on the cancellous bone tissue can lead to resorption, a phenomenon in which the density and mass of the cancellous tissue decreases, eroding support for the implant.
U.S. Pat. No. 5,611,688 to Hanosh describes a tooth replacement with an expanding implant member. The inserted, or distal portion of the implant member is arranged to expand outwardly into the surrounding cancellous bone.
U.S. Pat. No. 5,951,288 to Sawa describes a tooth replacement with an implant member formed of a shape-memory alloy which is maintained at a cool temperature for easy and non-traumatic insertion. Once in place, the implant member warms to body temperature and expands to anchor itself within the cancellous bone.
U.S. Pat. No. 6,015,294 to Lauks describes a tooth replacement with an implant member having a relatively short cylindrical section and a plurality of wedges extending from the distal portion of the cylindrical section and penetrating the cancellous bone.
These patents, while claiming to solve prior-art problems, still rely on anchoring of the implant member with respect to the cancellous bone, and are generally too deep for those people for whom there is a risk of contact with the mandibular canal or the sinus cavity.
U.S. Pat. No. 5,702,346 to Lazzara describes a tooth replacement with an implant member having a width that is substantially the same as the distance between the cortical plates at the site of installation, so that when the implant member is installed, it is anchored with respect to the cortical plates. However, in general, the bore in the bone is not symmetric, with respect to the two cortical plates, so it is nearly impossible for the center of the bore to be at equal distances from the two cortical plates. Therefore, there may be situations in which Lazzara""s implant member is anchored only with respect to one cortical plate, causing an unbalanced load distribution. Furthermore, there may be sections of the bone where the cortical plates close in, and the distance between them narrows. These sections are called undercuts. If an implant member is forced passed undercuts, the cortical plates may crack or puncture.
U.S. Pat. No. 3,981,079 to Lencyzycki describes a tooth replacement wherein the implant member has at least one pre-formed partially threaded lateral channel and is anchored with respect to the buccal cortical plate with at least one lateral screw. The implant member may be hollow or solid. For example, the implant member may be a hollow cylinder, and the partially threaded lateral channel may be two orifices on opposite walls of the cylinder. The distal orifice, with respect to the operator and the buccal cortical plate, has an internal thread, and the proximal orifice has a smooth internal surface, but with a diameter that is slightly larger than that of the distal orifice. Generally, the lateral screw is threaded, self-tapping its way into a lateral channel in the buccal cortical plate and a portion of the cancellous bone tissue. The lateral screw passes freely through the proximal orifice and is threaded into the distal orifice. The lateral screw then advances into the bone, beyond the distal orifice, self-tapping its way through the cancellous bone tissue. Thus the lateral screw is anchored with respect to the buccal cortical plate and with respect to the distal, threaded orifice, but not with respect to the lingual cortical plate.
This arrangement suffers from several drawbacks. Anchoring the implant member with respect to only one cortical plate creates an unbalanced, asymmetric load distribution on the jawbone. In addition, since the cortical plates are wood-like, having little elasticity, the fact that the lateral screw is threaded into both the implant member and the buccal cortical plate prevents re-adjustment and settling of the implant member and may lead to cracking of the cortical plate. The desirable situation is that which maintains the implant member in place, while providing some elasticity for re-adjustment.
U.S. Pat. No. 5,797,741 to Bombard et al. describes a tooth replacement with a solid implant member having a lateral key, whose function is similar to that of the lateral screw in U.S. Pat. No. 3,981,079, hereinabove. In a first embodiment, the lateral key is smooth and cylindrical, for easy insertion, and is arranged to pass through lateral channels, drilled in advance in the jawbone, and through the implant member. The lateral key is thus anchored with respect to the two cortical plates, and load distribution is generally symmetric on the jawbone. However, the tooth replacement described by U.S. Pat. No. 5,797,741 is applicable to the anterior portion of the mouth and would be difficult to install in the posterior portion.
The use of a smooth lateral key has some additional drawbacks:
1. For its insertion, the lateral key is tapped with a mallet, from the buccal side, into the channel drilled in the buccal cortical plate, through the implant member, and into the channel drilled in the lingual cortical plate. The tapping may cause a crack or an incipient crack in the lingual cortical plate. Such a crack is unlikely to be detected; yet it may lead to a loss of stability for the implant.
2. To facilitate its insertion, the lateral key must be, slightly smaller than the lateral channels in the jawbone, giving the implant member a certain freedom of movement. Indeed, with time, the bone tissue will grow and surround the implant member and the lateral key. However, during the initial period, before bone growth occurs, implant movement and play can damage the cancellous bone tissue and cause resorption, resulting in implant failure.
In a second embodiment, the lateral key has a threaded distal end, with respect to the operator and the buccal cortical plate, and is arranged to pass through a lateral channel in the buccal cortical plate and the cancellous bone tissue and into a blind, internally threaded channel in the implant member. In essence, this arrangement is similar to that of U.S. Pat. No. 3,981,079, hereinabove, and suffers from similar drawbacks, namely, that anchoring the implant member with respect to only one cortical plate creates an unbalanced, asymmetric load distribution on the jawbone. The locking of the implant member with the buccal cortical plate may cause a pulling action towards the buccal cortical plate. Additionally, it prevents re-adjustment and settling of the implant member. It can also result in cracking of the buccal cortical plate.
Additionally, both U.S. Pat. Nos. 3,981,079 and 5,797,741 use templates which are supported by superstructures of their respective implant members, for drilling lateral channels through the jawbone. However, these templates are held in place by implant members that have not been anchored to the cortical plates and are fixed in place only by the cancellous bone tissue. Therefore, the templates themselves are subject to movement and play, which the soft, cancellous bone tissue permits. In consequence, the positioning afforded by these templates may be inaccurate, and a lateral screw or key may not slide easily into a lateral channel, as expected. Instead, its insertion may be traumatic to the patient, and may even lead to bone damage that can affect the success of the implants.
There are other patents which use lateral screws, anchored with respect to a cortical plate, to support an implant member, for example, U.S. Pat. Nos. 3,436,826 and 4,084,318.
It is an aim of the present invention to provide a tooth replacement, having an implant member, anchored with bi-cortical anchor apparatus that has been uniquely designed to provide optimum bi-cortical stability and retention. When an implant member is anchored bi-cortically, loads are transferred to the hard, cortical bone that provides it with primary stabilizationxe2x80x94stabilization during the initial stage, before bone growth around the implant occurs. Additionally, an implant member anchored bi-cortically is capable of withstanding masticatory forces even in poor quality bones. Furthermore, because of the bi-cortical retention, an implant member that is inserted into the jawbone only to a depth of about 4-7 mm is possible, thus avoiding the mandibular canal. Bi-cortical retention may also be used for an implant member of greater depths, for example, 10-18 mm, when desired.
There is thus provided in accordance with a preferred embodiment of the present invention a bi-cortical anchor apparatus, arranged for insertion into a jawbone, from a proximal cortical plate towards a distal cortical plate. The bi-cortical anchor apparatus includes a distal portion, having a distal effective diameter and a distal surface which can bite into and engage with virgin tissue of the distal cortical plate, anchoring tightly to the plate. It also includes a mid portion, having a mid-portion effective diameter and a mid-portion surface which can support an implant member without locking. The apparatus further includes a proximal portion, having a proximal effective diameter, which is somewhat larger than both the distal and mid-portion effective diameters, and which has a proximal surface which can bite into and engage with virgin tissue of the proximal cortical plate, anchoring tightly to the plate. Finally, the apparatus includes a tool receptor at the proximal-most end of the proximal portion for interacting with a tool to facilitate the insertion of the apparatus.
There is further provided in accordance with a preferred embodiment of the present invention a bi-cortical anchor apparatus, arranged for insertion into a jawbone, from a proximal cortical plate towards a distal cortical plate. The bi-cortical anchor apparatus includes a distal portion, having a distal effective diameter and a distal surface, which can bite into and engage tissue of the distal cortical plate, anchoring tightly to the plate. The anchor apparatus further includes a mid portion, having a mid-portion effective diameter and a mid-portion surface, which can support an implant member without locking. The apparatus also includes a proximal portion, having a proximal effective diameter and a proximal surface which can bite into and engage a tissue of the proximal cortical plate, anchoring tightly to the plate. Finally, the anchor apparatus includes a tool receptor at the proximal-most end of the proximal portion for interacting with a tool to facilitate the insertion of the apparatus.
In yet another embodiment of the bi-cortical anchor apparatus, the distal portion, the mid portion and the proximal portion are machined as a single portion and have the same surface and the same effective diameter.
In another embodiment of the bi-cortical anchor apparatus, the mid portion includes a smooth surface.
In a further embodiment of the bi-cortical anchor apparatus, the proximal and distal effective diameters are substantially the same, and the mid portion effective diameter is somewhat smaller.
Additionally, in an embodiment of the bi-cortical anchor apparatus, the distal surface, which can bite into and engage with the tissue or virgin tissue of the distal cortical plate, anchoring tightly to the plate, has a threaded surface having at least one complete revolution.
In an embodiment of the invention, the proximal surface of the bi-cortical anchor apparatus bites into and engages the tissue or virgin tissue of the proximal cortical plate, anchoring it tightly to the plate. The proximal surface is a threaded surface having at least one complete revolution.
In another embodiment of the bi-cortical anchor apparatus, the distal surface bites into and engages with the tissue or virgin tissue of the distal cortical plate, anchoring it tightly to the plate. The distal surface is a tapping tool surface. In yet another embodiment, the proximal surface is a tapping tool surface.
In yet another embodiment of the bi-cortical anchor apparatus, the anchor apparatus completely penetrates the distal cortical plate while anchoring into the plate, so as to be flush with the external surface of the distal cortical plate.
In still another embodiment of the bi-cortical anchor apparatus, the anchor apparatus partially penetrates the distal cortical plate, while anchoring into the plate.
Another embodiment of the bi-cortical anchor apparatus has the anchor apparatus arranged for insertion so as to be flush with the external surface of the proximal cortical plate.
Additionally, in another embodiment of the bi-cortical anchor apparatus, the apparatus further includes a head at the proximal-most end, external to the proximal cortical plate, where the head includes the tool receptor.
In yet another embodiment, the tool receptor of the bi-cortical anchor apparatus is arranged to interact with a tool selected from a group which consists of an Ellen key, a screwdriver and a wrench.
Another embodiment of the bi-cortical anchor apparatus, includes a tool receptor which is a threaded internal cervix arranged to interact with a tool. The tool has proximal and distal portions with respect to the operator and a threaded surface at the distal portion which complements the threaded internal cervix. The tool has a finger-gripping portion at the proximal portion and a stem, connecting the proximal and distal portions, whereby the tool can guide the apparatus through a template drill-bit guide channel.
In another embodiment, the tool receptor of the bi-cortical anchor apparatus is arranged to interact with a tool, which can guide the apparatus through a template drill-bit guide channel.
Another embodiment of the bi-cortical anchor apparatus can come in various lengths to accommodate jawbones of different widths.
In yet another embodiment, the bi-cortical anchor apparatus can come in a range of effective diameters, the effective diameters selected from a group which consists of the distal effective diameter, the mid-portion effective diameter and the proximal effective diameter.
A further embodiment of the bi-cortical anchor apparatus includes a gradual increase in the diameter between the mid-portion and proximal effective diameters.
There is additionally provided in accordance with a preferred embodiment of the present invention an implant member arranged for insertion into a jawbone along a vertical axis of a tooth. The implant member includes near and far portions and a cervix, at the near portion, arranged so as to secure a dental prosthesis. The member also includes a through conduit, at the far portion, arranged to support a bi-cortical anchor apparatus, without locking. The conduit is separated from the cervix with a solid barrier which acts as a bacteria barrier. The member includes a bi-cortical anchor apparatus, arranged for insertion into a jawbone, from a proximal cortical plate towards a distal cortical plate. The bi-cortical anchor apparatus includes a distal portion, having a distal effective diameter and a distal surface, which can bite into and engage with virgin tissue of the distal cortical plate, anchoring tightly to the plate. The bi-cortical apparatus also includes a mid portion, having a mid-portion effective diameter and a mid-portion surface, which can support an implant member without locking. The apparatus includes a proximal portion, having a proximal effective diameter, which is somewhat larger than both the distal and mid-portion effective diameters. The proximal portion has a proximal surface which can bite into and engage virgin tissue of the proximal cortical plate, anchoring tightly to the plate. Finally the apparatus has a tool receptor, at the proximal-most end of the proximal portion, for interacting with a tool, to facilitate the insertion of the apparatus.
Also provided, in accordance with a preferred embodiment of the present invention is an implant member, arranged for insertion into a jawbone. The implant member includes near and far portions, and a cervix, at the near portion, arranged to secure a dental prosthesis. The implant member further includes a through conduit, at the far portion, arranged to support a bi-cortical anchor apparatus without locking. The through conduit is separated from the cervix with a solid barrier, which acts as a bacteria barrier. The bi-cortical anchor apparatus is arranged for insertion into a jawbone, from a proximal cortical plate towards a distal cortical plate. The bi-cortical anchor apparatus includes a distal portion, having a distal effective diameter and a distal surface, which can bite into and engage with a tissue of the distal cortical plate, anchoring tightly to the plate. The anchor apparatus further includes a mid portion, having a mid-portion effective diameter and a mid-portion surface, which can support an implant member without locking. The anchor apparatus also includes a proximal portion, having a proximal effective diameter and a proximal surface which can bite into and engage with a tissue of the proximal cortical plate, anchoring tightly to the plate. Finally, the anchor apparatus includes a tool receptor, at the proximal-most end of the proximal portion, for interacting with a tool, to facilitate the insertion of the apparatus.
In yet another embodiment, the through conduit of the implant member has a smooth internal surface. In still another embodiment, the implant member defines a z-axis along the vertical axis of the tooth, an x-axis, in any one of the buccal to lingual and buccal to palatal directions, and a y-axis, perpendicular to the x- and z-axes. The through conduit is slanted with respect to an axis selected from a group which consists of the x-, y-, and z-axes,
Additionally, in an embodiment of the invention, the through conduit of the implant member is an open through conduit.
In an embodiment of the invention, the implant member is arranged for insertion to a depth in a range between 4 and 18 mm. In another embodiment, it is arranged for insertion to a depth of 5 to 7 mm.
In another embodiment of the invention, the implant member further includes a threaded external surface for self-tapping an internal thread into the bone tissue during insertion.
In yet another embodiment, the implant member is arranged as a maxillary implant member which reaches into the sinus cavity.
Additionally, in another embodiment, the implant member further includes a mini-plate to increase the anchoring of the bi-cortical anchor apparatus to the proximal cortical plate.
In another embodiment, the implant member further includes at least one screw to increase the anchoring of the mini-plate to the proximal cortical plate.
The implant member in another embodiment of the present invention further includes a complementary template for guiding a drill bit from the proximal cortical plate into the through conduit.
There is also provided, in accordance with a preferred embodiment of the present invention, a complementary system, which includes an implant member having a portion which protrudes from the jawbone, when the implant member is installed in the jawbone. The implant member also has a through conduit at a far portion with respect to an operator, invisible to the operator, when the implant member is installed in the jawbone. The complementary system also has a template, having a distal vertical section, running generally along a distal cortical plate of the jawbone, so as to press against the distal cortical plate. The template also has a proximal vertical section, running generally along a proximal cortical plate of the jawbone. The proximal vertical section includes a drill-bit-channel housing and a drill-bit guide channel, located within the drill-bit-channel housing. The template also includes a lateral section, arranged to mesh with the portion of the implant member which protrudes from the jawbone, thereby aligning the drill-bit guide channel with the through conduit of the implant member.
In another embodiment of the present invention, the drill-bit guide channel of the complementary system guides the bi-cortical anchor apparatus for insertion into the jawbone.
In yet another embodiment of the complementary system, the portion which protrudes from the jawbone is a mount that is provided with the implant member.
Additionally, in another embodiment of a complementary system according to the present invention, the portion, which protrudes from the jawbone is a superstructure of the implant member.
In yet another embodiment of a complementary system, the system further includes a slide mechanism for adjusting to jawbones of different widths.
In an embodiment of a complementary system according to the present invention, the system further includes at least one spike arranged for piercing a cortical plate selected from a group which consists of the distal cortical plate and the proximal cortical plate, for increasing the hold on the jawbone. In some systems, the at least one spike is a plurality of spikes.
In yet another embodiment of a complementary system according to the present invention, the drill-bit-channel housing is formed as a hollow bolt, arranged to selectably press against the proximal cortical plate.
In a further embodiment of the present invention, the drill-bit guide channel of a complementary system is located within the hollow bolt, and further guides the bi-cortical anchor apparatus for insertion into the jawbone.
Additionally, in another embodiment of a complementary system according to the present invention, the distal vertical section runs generally along the distal cortical plate of the jawbone, the section pressing against the plate. The distal vertical section is a leaf spring.
Yet another embodiment of a complementary system further includes a ratchet which is arranged to clamp the template and the distal cortical plate. The distal vertical section runs generally along the distal cortical plate of the jawbone, pressing against it and acting as a distal prong of the ratchet. In yet another embodiment, the ratchet further includes a locking mechanism arranged for jawbones of different widths.
In other embodiments of a complementary system, the ratchet is a three-prong ratchet, having two proximal prongs, to the left and to the right of the drill-bit guide channel housing, along the y-axis, and having a single distal prong.
In embodiments of the present invention, the implant member of the complementary system is constructed in one of the ways described above.
There is also provided, in accordance with a preferred embodiment of the present invention, a method of installing an implant member which includes the steps of drilling a bore from the bone crest into the jawbone and inserting an implant member, having a through conduit, into the bore. The method then includes positioning a template, while meshing a lateral section of the template with a portion of the implant member which protrudes from the jaw, thus aligning a drill-bit guide channel with the through conduit of the implant member. This is followed by drilling a channel in the jawbone, through the drill-bit guide channel of the template and inserting a bi-cortical anchor apparatus from the proximal cortical plate through the bone channel and then through a conduit of the implant member, towards the distal cortical plate, for bi-cortical retention, while self-tapping an internal thread in the bone channel. Anchoring the distal portion of the bi-cortical anchor apparatus thus is effected by biting into tissue of the distal cortical plate, engaging the plate. The method also includes the step of anchoring the proximal portion of the bi-cortical anchor apparatus by biting into tissue of the proximal cortical plate and engaging that plate.
In a further embodiment of the present invention, a method is provided where the step of positioning further includes the step of pressing a hollow bolt, which houses the drill-bit guide channel, against the proximal cortical plate.
Yet another embodiment of the present invention provides a method where the step of inserting the bi-cortical anchor apparatus further includes the step of inserting through the drill-bit guide channel without moving the template. This step occurs between the step of drilling a channel in the jawbone and the step of inserting the bi-cortical anchor apparatus.
In still another embodiment of the present invention, a method is provided where clamping the jawbone between proximal and distal vertical sections of a template further includes clamping between a proximal vertical section of the template and at least one distal leaf spring.
Additionally, in another embodiment of the present invention, a method is provided where clamping the jawbone between proximal and distal vertical sections of a template further includes clamping with a ratchet.
Another embodiment of the present invention provides a method where clamping the jawbone between proximal and distal vertical sections of a template further includes piercing at least one cortical plate with spikes.
Yet another embodiment of the present invention provides a method which further includes the step of employing a mini-plate to increase the anchoring of the bi-cortical anchor apparatus to the proximal cortical plate.
In still another embodiment of the present invention, a method is provided where drilling a bore from the bone crest into the jawbone further includes drilling a bore from bone crest into the sinus cavity.
In another embodiment of the present invention, a method is provided which further includes employing a mini-plate to increase the anchoring of the bi-cortical anchor apparatus to the proximal cortical plate.
Another embodiment of the present invention provides a method which further includes employing at least one screw to increase the anchoring of the mini-plate to the proximal cortical plate.
In yet another embodiment of the present invention, a method is provided which further includes adjusting to jawbones of different widths.